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These carnivorous sponges wield lethal weapons made of glass

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25 May 2017 - 9:52pm

Three carnivorous sponges found in the beam trawl on the RV Investigator voyage to Australia's eastern abyss. From left to right: Cladorhiza, Abyssocladia, and something referred to affectionately as 'sponge on a rope'. Images: Karen Gowlett-Holmes

Day 11: Merrick Ekins, Queensland Museum

In our beam trawls we have found some fantastic carnivorous sponges: micro predators only five to 15 centimetres long.

Sponge spicules.

Sponges are very cool animals. Firstly they are silicon based, so they have amazing pure silicon (glass) spicules ranging from the microscopic (see picture) to ones up to a metre long. Secondly, sponge cells are totipotent, that is, each cell can behave like a stem cell and go on to become any other type of cell that is required. In the case of the carnivorous sponges, the new cell can migrate to the prey and individually digest little crustaceans.

We have collected species of Abyssocladia, sponges that resemble a bottlebrush, and Cladorhiza, which resemble parasols. These types of sponges have been reported previously to be carnivorous as they tend to get small crustaceans hooked on their Velcro-like spines to be slowly digested in-situ. This technique differs from most deep-sea sponges, which feed on bacteria and other single-celled organisms filtered from passing currents.

I need to examine the spicules of these specimens to see if I can identify them, but first I will have a look under the dissection microscope to see whether their spicules have snared any prey.

Merrick demonstrates the size of a glass sponge he hopes to find in the next beam trawl. Image: Asher Flatt